1. Field of the Invention
The present invention relates to an endoscopic imaging apparatus being mounted on an endoscope, having an outer metallic sheathing thereof coupled hermetically to a housing frame of a connector via an insulating hermetic member, having a shielded solid-state imaging device stowed in an internal hermetic space, and being capable of being autoclaved.
2. Description of the Related Art
An endoscopic imaging apparatus mounted on an endoscope to be inserted into a body cavity and having an imaging device incorporated therein is an electrical equipment whose electrical safety is guaranteed. A patient circuit (or an equivalent) is isolated from a housing metallic member.
In recent years, there has been concern about the environment; therefore, it has become increasingly desirable to be able to autoclave an endoscopic imaging apparatus under high-temperature and high-pressure steam without the use of any additional agents.
For example, Japanese Unexamined Patent Publication No. 7-100104 or 7-100102 has disclosed an endoscopic imaging apparatus capable of being autoclaved. In this prior art, a camera head is formed with a three-layered sheathing member composed of a metallic layer, insulating layer, and conductive layer in that order from the outside and is thus structured to be adiabatic.
In the camera head capable of being autoclaved, a housing thereof is structured to be hermetically sealed. In this case, the housing is made of a metal selected upon consideration of its heat resistance, steam resistance, and coefficient of thermal expansion.
In practice, care must be taken upon use of a cautery knife and to provide a guarantee of safety. For an endoscopic imaging apparatus including an electrical circuit, therefore, a structure of isolating the internal circuit from a housing of a camera head in order to ensure isolation from a rigid endoscope with a metallic housing is usually adopted.
Moreover, a patient circuit (or an equivalent) must be provided with a shielding structure having a potential of O V in order to solve a problem arising from coping with electromagnetic interference or from ensuring electromagnetic compatibility (EMC).
Consequently, the patient circuit (or an equivalent) and metallic housing must be isolated from each other. Moreover, they must be sealed hermetically. Conventionally, airtightness is attained using an adhesive or the like. The thus attained airtightness is deteriorated by steam.